For those who are trying to run their systems (based on the Asus A8N SLI Deluxe mobo) with 1:1 ratio at high HTT/mem clock speeds, say 250 Mhz - 255 Mhz, I think this might help you a little bit:
1) Flash/update your BIOS to 1006 revision: I do recommend this Bios and not the last one, 1007, because after testing it the results were frustrating. Summing up, my system would not even load Windows with the same config I have been using for weeks with great stability under Bios 1006.This was/is my everyday settings:
- HTT 252 Mhz
- CPU: vcore:1,425
Multiplier: 9´5x 252 x 9´5 = 2400 Mhz
- RAM Memory: DDR 400 must be selected in Bios in order to achieve 1:1 ratio
Timings: 2.5-3-3-7 1T
vdimm: 2.75v
- Hyper Transport Multiplier: 4x
- PCI Express Clock: 100 Mhz
- PCI Clock synchronization mode: 33´33Mhz
2) Enter the Bios and FIRST go to ADVANCED > CPU CONFIGURATION > DRAM CONFIGURATION: Here the values you should not change or vary are these:
- Hyper Transport Frequency: 4x
- Max MemClock : DDR400
- 1T/2T Memory Timing: 1T
The memory timings is a very particular matter: You should already know the capabilities of your Ram memory, if not, please, ask or get informed somehow.
I am telling you this because I do not recommend you to let the timings on AUTO mode since the motherboard sets very relaxed timings usually and that means lower performance, that?s why you should know the overclocking potential of your Ram modules as well as their aproppriate timings.
We are trying to get a 250 Mhz mem clock, that?s a PC4000 (500 Mhz) Ram memory module, if you own one of those simply check out the manufacturer?s specified timings and set them in the Bios.
Entering the RAM timings in the Bios: For the rookies this may be tricky that?s why I am going to explain you the following: Imagine you have a DDR memory module with these timings printed on your ram 2´5-3-3-7 The first number (2´5) always represents CAS Latency (?Tcl? in Bios) as it's usually the most important. The second number (3) represents RAS-to-CAS Delay (?Trcd in Bios?), the third one (3) represents Row Precharge Time (?Trp? in Bios) and the last one (7) represents the Min RAS Active Time (?Tras? in Bios) (which is always the final, and largest number). So, be careful when setting the timings!!
3) Afterwards, go to ADVANCED > JUMPERFREE CONFIGURATION:
Set the Overclock profile to Manual
CPU Frequency: rise it to 240-255 Mhz (as desired, the one your ram and chipset supports)
PCI Express Clock: 100 Mhz (always)
DDR Voltage: depends on your RAM modules (Do not go over 2.85v if you are not sure of your Ram specs/capabilities)
CPU Multiplier: This is the clue!!! After tough testings, it seems when working with 1:1 mode the only stable Cpu multipliers for this board are the decimal ones, I mean, non integer numbers as multipliers (ex: 7´5, 8´5, 9´5)
This ?rule? applies to HTT frequencies beyond 240 Mhz, for the low ones integer multipliers (7, 8, 9, 10) also work.
Recommended CPU Multipliers: 7´5, 8´5, 9´5 (all tested)
CPU Voltage: This depends on the actual Cpu speed, anyway;
References: 2´2 Ghz: 1´4125v (tested)
2´4 Ghz: 1´425v (tested)
2´6 Ghz: 1´5v (not tested)
PCI Clock Synchronization mode: 33´33 Mhz (always)
Last but not least, Go to BOOT > BOOT SETTINGS CONFIGURATION: Here in OS Select DRAM > 64 Mb, select OS2 if you have more than 64 Mb of RAM memory installed on your computer.
EXIT AND SAVE CHANGES
START TESTING: I would suggest you to begin searching for the highest HTT your Ram/Chipset supports in 1:1 mode. For this purpose, start with a HTT speed of 240 Mhz with a 7´5 Cpu multiplier with stock cpu voltage and go rising it if your system is stable!
Good luck
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